JP3639231B2 - Alignment apparatus and alignment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an alignment apparatus and an alignment method, and more particularly to an apparatus and an alignment method for aligning two objects that are opposed to each other with a minute gap therebetween.
[0002]
[Prior art]
In X-ray exposure and electron beam exposure, proximity exposure is generally used. In the proximity exposure, the mask and the wafer are arranged with a small gap (proximity gap) therebetween, and the wafer surface is irradiated with X-rays or electron beams through the mask. The alignment between the mask and the wafer is performed by simultaneously observing the alignment mask mark formed on the mask and the alignment wafer mark formed on the wafer and detecting the amount of positional deviation between them. Is called.
[0003]
[Problems to be solved by the invention]
During alignment, the wafer mark is observed through the mask. There is no particular problem when the mask transmits visible light sufficiently, but when the visible light transmittance is low, a sufficiently bright image cannot be obtained, and alignment becomes difficult. Further, when adjusting the gap between the wafer and the mask, the wafer may come into contact with the mask and the mask may be damaged.
[0004]
An object of the present invention is to provide an alignment apparatus and an alignment method that can be easily aligned even when the transmittance of the mask is low and are less likely to cause damage to the mask.
[0005]
[Means for Solving the Problems]
  According to one aspect of the present invention, the first holding means for holding the first object on which the first mark is formed on the first surface and the second mark on the second surface are formed. A second holding means for holding the second object and a second surface of the second object held by the second holding means are held by the first holding means. When viewed from a first position arranged with a gap from the first surface of the object and a line of sight parallel to the normal direction of the first surface, the second object is held by the second holding means. A moving mechanism for moving the second holding means to a second position where at least a part of the second object does not overlap the first object held by the first holding means; The first mark of the first object held by the first holding means;, Relating to a direction parallel to the first surfacepositionAs well as measuringWhen the second holding means is in the first position, the second mark on the second surface of the second object held by the second holding means, In a direction parallel to the second surfaceWhen the first measuring device for measuring the position and the second holding means are in the second position, the second surface of the second object held by the second holding meansWith respect to a direction parallel to and perpendicular toOne of a second measuring device that measures the position of the second mark, the first object held by the first holding means, and the second object held by the second holding means An alignment device is provided having a fine adjustment mechanism that is displaced relative to the other.
[0006]
The second holding means holds the member on which the reference mark is formed. When the second holding means is arranged at the first position, and when the second holding means is arranged at the second position, Detect position. By associating the positional information of the two, the second holding means is obtained from the position information of the second mark when the second holding means holds the second object and is arranged at the second position. It is possible to know the position of the second mark when is moved to the first position. As a result, the relative positional relationship between the first object and the second object, which would occur when the second holding means is moved from the second position to the first position, Can be adjusted in a state where the holding means is arranged at the second position.
[0007]
  According to another aspect of the present invention, (a) the third holding means is arranged at the third position, and the position of the reference mark fixed to the third holding means is measured by the third measuring device. And (b) the third holding means, Move in a direction parallel to the XY plane4th positionPlaced inA step of measuring the position of the reference mark fixed to the third holding means by a fourth measuring device, and (c) based on two pieces of position information of the reference mark obtained in the step, Obtaining positional relationship information associating positional information measured by the third measuring device with positional information measured by the fourth measuring device; and (d) disposed at the third position. Holding the fourth object by the fourth holding means so as to face the third object held by the third holding means at a time with a certain gap, and (e) First3Measuring the position of the fourth mark on the fourth object held by the fourth holding means, and (f) using the third holding means to measure the third object. Holding and moving the third holding means to the fourth position; and (g) holding the third holding means in the state where the third holding means has moved to the fourth position. Measuring the position of the third mark formed on the third object formed by the fourth measuring device; and (h) the third holding means.Move in a direction parallel to the XY planeSaid third positionTo placeIn addition, based on the position information of the third mark and the positional relationship information, one of the third object and the fourth object is moved relative to the other, and the both are aligned. ProcessIn the step (a), the position of the reference mark is measured with respect to a direction parallel to the XY plane and a Z direction perpendicular to the XY plane, and in the step (g), a direction parallel to the XY plane. , And the position of the third mark with respect to the Z direction perpendicular to the XY plane, and in the step (h), alignment is performed with respect to the direction parallel to the XY plane and the Z direction.An alignment method is provided.
[0008]
The position of the third mark is detected in a state where the third holding means is arranged at the fourth position. In this state, the fourth object is not disposed opposite to the third object. For this reason, the third mark can be observed without being blocked by the fourth object.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Before describing the embodiment of the present invention, the previous proposal of the present inventor related to the embodiment will be described with reference to FIGS.
[0010]
FIG. 1 shows a schematic diagram of a position detection apparatus according to the previous proposal. The previously proposed position detection apparatus includes a wafer / mask holding unit 10, an optical system 20, and a control device 30.
[0011]
The wafer / mask holder 10 includes a wafer holder 15, a mask holder 16, and fine adjustment mechanisms 17 and 18. At the time of alignment, the wafer 11 is held on the upper surface of the wafer holding table 15 and the mask 12 is held on the lower surface of the mask holding table 16. The wafer 11 and the mask 12 are arranged substantially in parallel so that a certain gap is formed between the exposure surface of the wafer 11 and the wafer side surface (mask surface) of the mask 12. A wafer mark for alignment is formed on the exposure surface of the wafer 11, and a mask mark for alignment is formed on the mask surface of the mask 12.
[0012]
The fine adjustment mechanism 17 can move the wafer holding table 15 or the mask holding table 16 so that the relative position of the wafer 11 and the mask 12 in the exposure plane changes. The fine adjustment mechanism 18 can move the wafer holder 15 so that the distance between the exposure surface of the wafer 11 and the mask surface of the mask 12 changes. When the X axis is taken from the left to the right in the figure, the Y axis is directed from the front surface to the back surface in the direction perpendicular to the paper surface, and the Z axis is taken in the normal direction of the exposure surface, the fine adjustment mechanism 17 The relative position with respect to the axial direction, the Y-axis direction, and the rotational direction (θz direction) around the Z-axis is adjusted, and the fine adjustment mechanism 18 rotates (tilting) directions (θx and The relative position in the θy direction) is adjusted.
[0013]
The optical system 20 includes image detection devices 21A and 21B, lenses 22 and 28, half mirrors 23 and 26A, an optical fiber 24, and a mirror 26B. The optical axis 25 of the optical system 20 is arranged to be parallel to the ZX plane and oblique to the exposure surface.
[0014]
Illumination light emitted from the optical fiber 24 is reflected by the half mirror 23 to form a light bundle along the optical axis 25, and is obliquely incident on the exposure surface through the lens 22. The illumination light transmitted through the lens 22 becomes a parallel light beam or a convergent light beam.
[0015]
When the wafer mark and mask mark provided on the wafer 11 and the mask 12 have edges or vertices, the illumination light is scattered at the edges or vertices. Of the scattered light, light incident on the lens 22 is converged by the lens 22, and a part of the light passes through the half mirrors 23 and 26A and forms an image on the light receiving surface 29A of the image detection device 21A. The imaging magnification on the light receiving surface 29A is, for example, 20 times. Of the scattered light, the light reflected by the half mirror 26A is reflected by the mirror 26B, converged by the relay lens 28, and forms an image on the light receiving surface 29B of the image detection device 21B. The imaging magnification on the light receiving surface 29B is, for example, 80 to 100 times. Thus, two observation optical systems having different magnifications are arranged.
[0016]
The image detection devices 21A and 21B photoelectrically convert images of the scattered light from the wafer 11 and the mask 12 formed on the light receiving surfaces 29A and 29B, respectively, to obtain image signals. These image signals are input to the control device 30.
[0017]
The control device 30 processes the image signal input from the image detection devices 21 </ b> A and 21 </ b> B and detects the relative position between the wafer 11 and the mask 12. Further, a control signal is sent to the fine adjustment mechanisms 17 and 18 so that the wafer 11 and the mask 12 have a predetermined relative positional relationship. Based on this control signal, the fine adjustment mechanism 17 translates the mask holding table 16 in the XY plane and rotates it around the Z axis. Based on this control signal, the fine adjustment mechanism 18 translates the wafer holding table 15 in the Z-axis direction and slightly rotates it around the X-axis and the Y-axis.
[0018]
FIG. 2A is a plan view showing the relative positional relationship between the alignment wafer marks 13A and 13B and the mask mark 14 formed on the wafer 11 and the mask 12 of FIG. Wafer marks 13A and 13B are formed by arranging three rectangular patterns in the Y-axis direction and 14 in the X-axis direction in a matrix. One mask mark 14 is formed by arranging three similar rectangular patterns in the Y-axis direction and five in the X-axis direction in a matrix. In the state where the alignment is completed, the mask mark 14 is arranged at substantially the center between the wafer marks 13A and 13B in the Y-axis direction.
[0019]
The long sides of the rectangular patterns of the wafer marks 13A and 13B and the mask mark 14 are parallel to the X axis, and the short sides are parallel to the Y axis. The long side length of each rectangular pattern is 2 μm, for example, and the short side length is 1 μm, for example, and the arrangement pitch of the rectangular pattern in each mark in the X-axis and Y-axis directions is 4 μm. The distance between the centers of the wafer marks 13A and 13B is 56 μm.
[0020]
2B is a cross-sectional view taken along dashed-dotted line B2-B2 in FIG. Wafer marks 13A and 13B are formed, for example, by patterning a SiN film, a polysilicon film or the like formed on the exposure surface. The mask mark 14 is made of, for example, Ta formed on the mask surface of the membrane 12 made of SiC or the like._FourIt is formed by patterning the B film.
[0021]
FIG. 2C illustrates a cross-sectional view taken along one-dot chain line C2-C2 in FIG. The illumination light incident on the wafer marks 13A and 13B and the mask mark 14 along the optical axis 25 is scattered at the short-side edge of each rectangular pattern in FIG. The light applied to the region other than the edge is regularly reflected and does not enter the lens 22 in FIG. Accordingly, only the scattered light from the edge can be detected by the image detection devices 21A and 21B. Here, regular reflection refers to reflection in such a manner that most components of incident light are reflected in the same reflection direction, and the reflection angle is equal to the incident angle.
[0022]
In the object space of the optical system 20 in FIG. 1, scattered light from a plurality of points on one plane perpendicular to the optical axis 25 is simultaneously imaged on the light receiving surfaces 29A and 29B of the image detection devices 21A and 21B. A plane in which object points in the object space that are imaged on the light receiving surfaces 29A and 29B are gathered is referred to as an “object surface”.
[0023]
In FIG. 2C, among the edges of the wafer marks 13A and 13B and the mask mark 14, the scattered light from the edge on the object surface 27 is focused on the light receiving surface, but from the edge not on the object surface. The scattered light is not focused, and as the edge moves away from the object surface, the image is not focused by the scattered light from the edge. Therefore, the image by the scattered light from the edge closest to the object surface among the edges of each mark becomes the clearest, and the image by the scattered light from the edge away from the object surface is blurred.
[0024]
FIG. 3 is a sketch of an image on the light receiving surface due to scattered light from the edge. The u axis in FIG. 3 corresponds to the direction of intersection between the object surface 27 and the ZX plane in FIG. 2C, and the V axis corresponds to the Y axis in FIG. Images 40A and 40B due to scattered light from wafer marks 13A and 13B appear apart in the v-axis direction, and image 41 due to scattered light from mask mark 14 appears therebetween.
[0025]
Since scattered light from the front edge and the rear edge of each rectangular pattern is observed, two dot images appear for one rectangular pattern. In each image, an image due to scattered light from an edge in the vicinity of the object surface 27 in FIG. 2C appears clearly, and then becomes a blurred image as the distance in the u-axis direction increases. Further, as shown in FIG. 2C, since the observation optical axis 25 is inclined with respect to the exposure surface, the most focused position of the images 40A and 40B due to the scattered light from the wafer mark and the mask mark. The position where the image 41 is most focused by the scattered light does not coincide with the u-axis direction.
[0026]
1 is moved by moving the wafer holder 15 and the mask holder 16 in FIG. 1 so that the image 41 due to the scattered light from the mask mark is positioned at the center of the images 40A and 40B in the v-axis direction. That is, the wafer 11 and the mask 12 can be aligned with respect to the direction of the line of intersection between the object surface and the exposure surface.
[0027]
In the position detection apparatus shown in FIG. 1, since the wafer mark and the mask mark are observed obliquely, it is not necessary to arrange the optical system 20 in the path of the energy beam 40 for exposure. For this reason, it is not necessary to retract the optical system 20 out of the exposure range during exposure. Further, when the wafer is exposed after the alignment is completed, the position can always be detected even during the exposure. Furthermore, since the illumination optical axis and the observation optical axis are coaxial, there is no axial shift and a stable image can be obtained at all times.
[0028]
4A and 4B show image signals obtained by the image detection device 21. FIG. The horizontal axis corresponds to the v-axis in FIG. 3, and the vertical axis represents the light intensity. This image signal is the most in-focus position of the image 41 and the scanning line at the position where the images 40A and 40B are in focus among the image signals obtained by scanning the light receiving surface shown in FIG. This is a composite of image signals corresponding to a scanning line at a position.
[0029]
4A shows a case where the wafer mark is made of polysilicon, and FIG. 4B shows a case where the wafer mark is made of SiN. Both mask marks are Ta_FourB is formed. As shown in FIGS. 4 (A) and 4 (B), three peaks corresponding to the mask mark appear approximately at the center, and three peaks corresponding to the wafer mark appear on both sides thereof.
[0030]
Hereinafter, an example of a method for detecting the relative position of the mask mark and the wafer mark from the waveform shown in FIG. 4A or FIG. 4B will be briefly described. First, the correlation coefficient with the peak waveform corresponding to each of the two wafer marks is calculated while shifting the peak waveform corresponding to the mask mark in the v-axis direction. The shift amount that gives the maximum correlation coefficient corresponds to the center-to-center distance between the wafer mark and the mask mark.
[0031]
The wafer and the mask are moved so that the intervals between the peak waveform corresponding to the mask mark and the peak waveform corresponding to each of the wafer marks on both sides thereof are equal to each other in the Y-axis direction of FIG. be able to.
[0032]
The two-dimensional image signal shown in FIG. 3 is translated in the u-axis direction and the v-axis direction, and similarity pattern matching between the mask mark image and the wafer mark image is performed, so that the wafer and the mask are aligned. The relative position may be obtained. By performing pattern matching of a two-dimensional image, the distance between images in the u-axis direction and the v-axis direction can be obtained.
[0033]
Next, a method for measuring the distance between the wafer and the mask will be described. In FIG. 3, a position u that is most focused in the u-axis direction in the images 40A and 40B due to scattered light from the wafer mark.₀Is an intersection line P between the object surface 27 and the exposure surface in FIG.₀It corresponds to. Further, in FIG. 3, the position u that is most focused in the u-axis direction in the image 41 by the scattered light from the mask mark.₁Is the intersection line P between the object surface 27 and the mask surface in FIG.₁It corresponds to. For example, the position u is obtained by pattern matching of the two-dimensional image shown in FIG.₀And u₁The distance between them can be determined.
[0034]
Line segment P₀P₁The length of L (P₀P₁), The distance δ between the wafer 11 and the mask 12 is
[0035]
[Expression 1]
δ = L (P₀P₁) × sin (α)
It is expressed. Here, α is an angle formed by the normal direction of the exposure surface and the optical axis 25. Therefore, the position u on the u-axis in FIG.₀And u₁Distance L (u₀u₁) To measure line segment P₀P₁The distance δ can be known by obtaining the length of.
[0036]
Instead of performing pattern matching between observed images, pattern matching with a reference image may be performed. In this case, a reference image signal in a state where the wafer and the mask are arranged so as to satisfy a desired relative positional relationship is stored in advance. The amount of deviation from the reference position of the wafer is obtained by performing similarity pattern matching between the observed wafer mark and the image of the wafer mark stored in advance. Similarly, the amount of deviation from the reference position of the mask is obtained. From the amount of deviation, the relative position of the wafer and the mask can be known.
[0037]
The accuracy required for alignment in the Y-axis direction shown in FIG. 1 is becoming stricter as the degree of integration of integrated circuit devices is improved. For example, in the case of a dynamic RAM having a storage capacity of 16 Gbits, an alignment accuracy of about 12.5 nm is required.
[0038]
In order to perform alignment based on the image signal shown in FIG. 4, it is preferable that the relative alignment between the wafer and the mask is within a certain error range. However, it is difficult to hold the wafer 11 shown in FIG. 1 on the wafer holder 15 and hold the mask 12 on the mask holder 16 with an accuracy that falls within this error range. For this reason, after holding the wafer 11 and the mask 12, it is preferable to perform rough alignment (coarse alignment) so as to be within this error range.
[0039]
This coarse alignment can be easily performed based on an image signal based on an image on the light receiving surface 29A having a low imaging magnification. After the course alignment is completed, more accurate alignment (fine alignment) can be performed based on the image signal of the image on the light receiving surface 29B having a high imaging magnification. By performing the coarse alignment before the fine alignment, the alignment accuracy required when holding the wafer and the mask is relaxed.
[0040]
Further, as the degree of integration increases, it is required to keep the distance between the wafer 11 and the mask 12 constant. This interval is, for example, about 10 to 20 μm in the case of X-ray exposure with a line width of 0.1 μm, and an accuracy of about ± 1 μm is required. An interval between the wafer and the mask is detected based on an image signal based on an image on the light receiving surface 29A having a low imaging magnification.
[0041]
FIG. 1 shows the case where the optical axis of the illumination light and the optical axis of the observation optical system coincide with each other. However, if the regular reflection light of the illumination light does not enter the lens 22 of the observation optical system 20, It is not always necessary to match the two optical axes.
[0042]
Next, the magnification correction amount detection method will be described with reference to FIG.
[0043]
FIG. 5 shows a schematic plan view of the wafer 11 and mask 12 to be aligned and the optical system. Consider an XY Cartesian coordinate system within the surface of the wafer to be exposed. On the surface of the wafer 11, the first and second X-axis wafer marks UX₁And UX₂Is formed. Both are arrange | positioned in the mutually different position regarding the X-axis direction. Further, the first and second Y-axis wafer marks UY are formed on the surface of the wafer 11.₁And UY₂Is arranged. Both are arranged at different positions with respect to the Y-axis direction.
[0044]
The mask 12 includes first and second x-axis mask marks MX.₁And MX₂, First and second Y-axis mask marks MY₁And MY₂Is formed. First and second X-axis mask mark MX₁And MX₂Are the first and second X-axis wafer marks UX, respectively.₁And UX₂The first and second Y-axis mask marks MY are arranged at positions corresponding to₁And MY₂Are the first and second Y-axis wafer marks UY, respectively.₁And UY₂It is arranged at a position corresponding to.
[0045]
These wafer marks and mask marks have the same configuration as that shown in FIG. Optical system 20X₁Is the first X-axis wafer mark UX₁And the first X-axis mask mark MX₁Amount of deviation Δx in the X-axis direction₁Observe. Optical system 20X₂Is the second X-axis wafer mark UX₂And the second X-axis mask mark MX₂Amount of deviation Δx in the X-axis direction₂Observe. Optical system 20Y₁Is the first Y-axis wafer mark UY₁And the first Y-axis mask mark MY₁Amount of deviation Δy in the Y-axis direction₁Observe. Optical system 20Y₂Is the second Y-axis wafer mark UY₂And second Y-axis mask mark MY₂Amount of deviation Δy in the Y-axis direction₂Observe. These optical systems 20X₁~ 20Y₂Each has the same configuration as the optical system 20 shown in FIG.
[0046]
Next, a method for detecting the magnification correction amount of the mask 12 will be described. First, each wafer mark UX₁~ UY₂And the corresponding mask mark MX₁~ MY₂Observe and coarsely align.
[0047]
Next, the deviation amount Δx₁, Δy₁, And Δy₂Measure. Deviation Δx₁Based on the above, the relative position of the wafer 11 and the mask 12 in the X-axis direction is adjusted. More specifically, the shift amount Δx₁The mask 12 is moved in the X-axis direction with respect to the wafer 11 so that becomes zero.
[0048]
Deviation Δy₁And Δy₂Based on the above, the relative position of the wafer 11 and the mask 12 in the Y-axis direction is adjusted. For example, (Δy₁+ Δy₂) / 2 is moved in the Y-axis direction with respect to the wafer 11 so that / 2 becomes zero. Further, the deviation amount Δy₁And Δy₂Based on the above, the relative position of the wafer 11 and the mask 12 in the in-plane rotation direction is adjusted. For example, tan^-1[(Δy₁-Δy₂) / Lx], the mask 12 is rotated in the in-plane direction by an angle obtained from the angle.
[0049]
As a result of the operations so far, the first X-axis wafer mark UX in the X-axis direction.₁The positions of the wafer 11 and the mask 12 are aligned with each other at the position where is formed. When the mask 12 is deformed due to thermal expansion or the like, at other positions, both positions are shifted by the amount of deformation of the mask. For the Y-axis direction, the first Y-axis wafer mark UY₁And second Y-axis wafer mark UY₂The positions of the wafer 11 and the mask 12 are aligned at a position substantially in the center of the position where the two are disposed.
[0050]
Next, the deviation amount Δx₂Measure. Deviation Δx₂Is not 0, the deviation Δx with respect to the length Lx₂Only the mask 12 is distorted in the X-axis direction. That is, Δx₂The magnification correction amount in the X-axis direction can be obtained from / Lx.
[0051]
Next, the deviation amount Δx₁, Δx₂, And Δy₁Measure. In the process so far, the deviation amount Δx₁Is set to 0, and the amount of deviation Δx at that time₂Therefore, it is not necessary to measure again. For the Y-axis direction, the deviation amount Δy₁Since the mask 12 is moved in the Y-axis direction after measuring the deviation amount Δy again.₁Need to be measured.
[0052]
Deviation Δy₁Based on the above, the relative position of the wafer 11 and the mask 12 in the Y-axis direction is adjusted. More specifically, the shift amount Δy₁The mask 12 is moved in the Y-axis direction with respect to the wafer 11 so that becomes zero.
[0053]
Deviation Δx₁And Δx₂Based on the above, the relative position of the wafer 11 and the mask 12 in the X-axis direction is adjusted. For example, (Δx₁+ Δx₂The mask 12 is moved in the X-axis direction with respect to the wafer 11 so that) / 2 becomes zero. Further, the deviation amount Δx₁And Δx₂Based on the above, the relative position of the wafer 11 and the mask 12 in the in-plane rotation direction is adjusted. For example, tan^-1[(Δx₁-Δx₂) / Ly], the mask 12 is rotated in the in-plane direction by an angle obtained from the above.
[0054]
By the operation so far, the first Y-axis wafer mark UY in the Y-axis direction is obtained.₁The positions of the wafer 11 and the mask 12 are aligned with each other at the position where is formed. When the mask 12 is deformed due to thermal expansion or the like, at other positions, both positions are shifted by the amount of deformation of the mask. For the X-axis direction, the first X-axis wafer mark UX₁And second X-axis wafer mark UX₂Are positioned approximately in the center of the positions where the wafer 11 and the mask 12 are aligned.
[0055]
Next, the deviation amount Δy₂Measure. Deviation Δy₂Is not 0, the amount of deviation Δy with respect to the length Ly₂Only the mask 12 is distorted in the Y-axis direction. That is, Δy₂The magnification correction amount in the Y-axis direction can be obtained from / Ly.
[0056]
When the magnification correction amounts in the X-axis direction and the Y-axis direction are obtained, the magnification correction of the mask 12 is performed based on the correction amounts.
[0057]
The magnification correction is performed, for example, by locally heating the mask to cause thermal deformation. By appropriately selecting the heating part, it can be deformed almost independently in the X-axis direction or Y-axis direction (Shimazu et al., “Proposal of alignment method by X-ray mask thermal deformation correction”, 58th autumn of 1997) (See Journal of Applied Physics Society, Proceedings, Lecture No. 4p-ZL-8, page 700). Alternatively, the mask may be deformed by applying external stress to the mask. Exposure is performed after correcting the magnification of the mask. Note that fine positioning may be performed again after the magnification correction.
[0058]
Next, an alignment apparatus according to an embodiment of the present invention will be described with reference to FIG.
[0059]
A linear guide 51 is attached on the base 50, and the moving mechanism 52 translates along the linear guide 51. The wafer holding table 15 is attached to the moving mechanism 52 via the fine adjustment mechanisms 17 and 18. A wafer holder 15 holds the wafer 11 on the upper surface thereof. A mask holding table 16 is disposed above the wafer holding table 15. The mask holding table 16 holds the mask 12 on the lower surface thereof. The configurations of the fine adjustment mechanisms 17 and 18, the wafer holding table 15, and the mask holding table 16 are the same as the configuration of the alignment apparatus proposed above shown in FIG. 1. In the alignment apparatus shown in FIG. 6, a coordinate system similar to the XYZ orthogonal coordinate system shown in FIG. 1 is considered. The linear guide 51 guides the moving mechanism 52 in a direction parallel to the Y axis.
[0060]
The moving mechanism 52 can move the wafer holding table 15 from the exposure position 53 where the wafer 11 faces the mask 12 to the retracted position 54. When the wafer holding table 15 is disposed at the retracted position 54, the wafer 11 held on the wafer holding table 15 does not overlap the mask 12 held on the mask holding table 16 when viewed in a line of sight parallel to the Z axis. Are arranged as follows.
[0061]
An optical system 20X above the mask holding table 16₁And 20X₂Is arranged. Optical system 20X₁And 20X₂Each of these is the same as the optical system 20 shown in FIG. In FIG. 6, only two optical systems are shown, but actually, as shown in FIG. 5, the four optical systems 20X₁, 20X₂, 20Y₁And 20Y₂Is arranged. These optical systems 20X₁, 20X₂, 20Y₁And 20Y₂Detects the position of the mask mark formed on the mask 12 and also detects the position of the wafer mark formed on the exposure surface of the wafer 11 with the wafer holder 15 placed at the exposure position 53. Since the method for detecting the positions of these marks has been described with reference to FIGS. 3 and 4, the description thereof is omitted here. Further, as described with reference to FIGS. 2C and 3, the gap between the mask 12 and the wafer 11 can be measured.
[0062]
  Note that FIG. 3 illustrates the case where the wafer mark images 40A and 40B and the mask mark image 41 are observed simultaneously, but it is not always necessary to observe both simultaneously. For example, an image of a wafer mark in a state where the mask 12 is not held on the mask holding table 16.40A and 40BObserve only the most in-focus positionu ₀ Is detected. Next, the mask 12 is attached, and an image of the mask mark41The most in-focus positionu ₁ Is detected. If the position (height) of the wafer 11 in the Z-axis direction does not change before and after the mask 12 is attached, the position u measured at different times.₀And u₁Thus, the gap between the mask 12 and the wafer 11 can be obtained. The positions in the X-axis direction and the Y-axis direction can also be measured at different times.
[0063]
Above the wafer holder 15 when the moving mechanism 52 is disposed at the retracted position 54, the optical system 60X₁, 60X₂, 60Y₁And 60Y₂Is arranged. Optical system 60X₁, 60X₂, 60Y₁And 60Y₂Are respectively optical systems 20X.₁, 20X₂, 20Y₁And 20Y₂It has the same configuration and function.
[0064]
Optical system 20X₁, 20X₂, 20Y₁, 20Y₂, 60X₁, 60X₂, 60Y₁And 60Y₂The measurement result is input to the control device 30. The control device 30 stores the measurement result in the storage device 30A. The storage device 30A is composed of, for example, a semiconductor memory. Further, the control device 30 controls the fine adjustment mechanisms 17 and 18 and the moving mechanism 52.
[0065]
Next, an alignment method according to an embodiment of the present invention will be described with reference to FIGS. 7 to 10 show the mask holding table 16, the wafer holding table 15, and the optical system 20X.₁, 20X₂, 20Y₁, 20Y₂, 60X₁, 60X₂, 60Y₁And 60Y₂It is a top view which shows arrangement | positioning.
[0066]
As shown in FIG. 7, a dummy wafer 55 is held on the wafer holding table 15 and placed at the exposure position 53. At this time, the mask is not yet held on the mask holding table 16. Four reference marks 56X on the surface of the dummy wafer 55₁56X₂56Y₁, And 56Y₂Is formed. Reference mark 56X₁56X₂56Y₁, And 56Y₂Each has a configuration similar to that of wafer marks 13A and 13B shown in FIG. 2A, and each of wafer marks UX shown in FIG.₁, UX₂, UY₁And UY₂Corresponding to Optical system 20X₁~ 20Y₂And each fiducial mark 56X₁~ 56Y₂Measure the position of.
[0067]
Hereinafter, fiducial mark 56X₁The other fiducial mark 56X₂56Y₁And 56Y₂The same procedure as described below is executed for.
[0068]
Reference mark 56X₁The X coordinate of the center of x₁And the height in the Z-axis direction is z₁And The wafer holder 15 is moved to the retracted position 54. Optical system 60X₁And fiducial mark 56X₁Measure the position of. Reference mark 56X₁X coordinate of x₂And the height in the Z-axis direction is z₂And When the wafer holder 15 is moved in the Y-axis direction, there is no displacement in the X-axis direction and the Z-axis direction, and the optical system 20X₁Observation coordinates and optical system 60X₁If the relative relationship with the observation coordinate has been adjusted, x₁= X₂And z₁= Z₂In general, x₁≠ x₂And z₁≠ z₂It becomes.
[0069]
The positional relationship information Δx and Δz are respectively expressed as Δx = x₁-X₂, Δz = z₁-Z₂It is defined as The positional relationship information Δx and Δz are stored in the storage device 30A shown in FIG. Reference mark 56X₁~ 56Y₂Then, the dummy wafer 55 is removed from the wafer holder 15.
[0070]
As shown in FIG. 8, the mask 12 is held on the mask holding table 16. Mask mark 57X on the mask surface of mask 12₁57X₂, 57Y₁, And 57Y₂Is formed. Mask mark 57X₁57X₂, 57Y₁, And 57Y₂Each has a configuration similar to that of the wafer mark 14 shown in FIG. 2A, and each of the mask marks MX shown in FIG.₁, MX₂, MY₁And MY₂Corresponding to
[0071]
Optical system 20X₁And mask mark 57X₁The position in the X-axis direction and the height in the Z-axis direction are measured. Mask mark 57X₁X coordinate of x₀, The height in the Z-axis direction is z₀Both are stored in the storage device 30A. Other mask mark 57X₂, 57Y₁, And 57Y₂The same procedure is performed for.
[0072]
As shown in FIG. 9, the wafer 11 is held on the wafer holding table 15 and placed at the retreat position 54. On the exposure surface of the wafer 11, a plurality of unit exposure areas 11A are defined. Position alignment and exposure are performed for each unit exposure region 11A.
[0073]
Four wafer marks 58X are provided in each unit exposure area 11A.₁, 58X₂, 58Y₁, And 58Y₂Is formed. Optical system 60X₁With wafer mark 58X₁Measure the position of. Wafer mark 58X₁X coordinate of x_Three, The height in the Z-axis direction is z_ThreeAnd Other wafer mark 58X₂, 58Y₁, And 58Y₂The same procedure is performed for.
[0074]
When the wafer holder 15 is moved to the exposure position 53, the wafer mark 58X₁And mask mark 57X₁The amount of displacement in the X-axis direction is x₀-(X_Three−Δx) and wafer mark 58X₁The size of the gap between the mask and the wafer at the position where is formed is z₀-(Z_Three−Δz). Similarly, wafer mark 58X₂And mask mark 57X₂Misalignment in the X axis direction, wafer mark 58Y₁And mask mark 57Y₁Misalignment in the Y-axis direction and the wafer mark 58Y₂And mask mark 57Y₂The amount of misalignment in the Y-axis direction is obtained. Further, the size of the gap between the wafer and the mask at the position where these marks are formed is obtained.
[0075]
From these pieces of information, the movement amount in the X-axis and Y-axis directions and the rotation angle in the θz direction for aligning the wafer and the mask can be obtained. Thereby, alignment of a wafer and a mask can be performed. The fine adjustment mechanisms 17 and 18 are operated in a state where the wafer holding table 15 is disposed at the retracted position 54 to perform alignment.
[0076]
As shown in FIG. 10, the wafer holding table 15 is moved to the exposure position 53. Since the alignment is performed at the evacuation position 54, the alignment between the wafer and the mask has already been completed with the wafer holder 15 moved to the exposure position 53.
[0077]
In the above embodiment, as shown in FIG. 9, the wafer mark can be directly observed without using a mask. For this reason, the position of the wafer mark can be easily detected even when the transmittance of the mask is low. In addition, since the alignment is performed in a state where the wafer holding table 15 is disposed at the retracted position 54, damage to the mask due to the wafer coming into contact with the mask can be prevented.
[0078]
In the above embodiment, the positional relationship information Δx and Δz is obtained using the dummy wafer 55, but it is also possible to obtain the positional relationship information Δx and Δz using a wafer to be actually exposed instead of the dummy wafer 55. For example, the positional relationship information may be obtained using a wafer to be processed first for each determined period. When processing the second and subsequent wafers, the mask and the wafer are aligned using the positional relationship information obtained using the first wafer.
[0079]
Next, an alignment apparatus according to another embodiment of the present invention will be described with reference to FIG.
[0080]
FIG. 11A shows a plan view of a wafer holding table of an alignment apparatus according to another embodiment and a target stage attached thereto, and FIG. 11B shows a cross-sectional view taken along one-dot chain line B11-B11. .
[0081]
As shown in FIG. 11B, the target stage 70 is attached to the wafer holding table 15 via a linear actuator 71 and a connecting member 73. The target stage 70 has a target surface 70 </ b> A that is parallel to the exposure surface of the wafer 11 held on the wafer holding table 15. The linear actuator 71 can be adjusted such that the target 70 is displaced in the Z-axis direction and the target surface 70 </ b> A is at the same height as the exposure surface of the wafer 11.
[0082]
As shown in FIG. 11A, the reference mark 72X is formed on the target surface 70A.₁, 72X₂72Y₁, And 72Y₂Is formed. These reference marks are the reference marks 56X formed on the dummy wafer 55 shown in FIG.₁~ 56Y₂Is the same. Reference mark 56X of dummy wafer 55 in the procedure described with reference to FIG.₁~ 56Y₂Reference mark 72X of target 70 instead of₁~ 72Y₂Can be used to obtain positional relationship information Δx and Δz. At this time, the height of the target surface 70 </ b> A is preferably set to the same height as the exposure surface of the wafer 11.
[0083]
Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0084]
【The invention's effect】
As described above, according to the present invention, the wafer mark formed on the exposure surface of the wafer can be directly observed without passing through the mask, and its position can be detected. In addition, since the gap between the wafer and the mask can be adjusted at the retreat position where the mask is not disposed, damage to the mask due to contact of the wafer with the mask can be prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an alignment apparatus according to a previous proposal.
FIG. 2 is a plan view and a cross-sectional view of a wafer mark and a mask mark.
FIG. 3 is a sketched image of scattered light from a wafer mark and a mask mark.
4 is a graph showing an example of an image signal of an image obtained by scattered light obtained by the position detection device shown in FIG. 1;
FIG. 5 is a plan view for explaining the arrangement of a wafer, a mask, and an optical system in the position detection apparatus according to the previous proposal.
FIG. 6 is a schematic sectional view of a main part of the alignment apparatus according to the embodiment.
FIG. 7 is a schematic plan view showing a positional relationship among a dummy wafer, a wafer holder for holding the dummy wafer, and an optical system for explaining an alignment method according to an embodiment.
FIG. 8 is a schematic plan view showing a positional relationship between a mask and an optical system for explaining an alignment method according to an embodiment.
FIG. 9 is a schematic plan view showing a positional relationship among a wafer, a wafer holder for holding the wafer, and an optical system for explaining an alignment method according to an embodiment.
FIG. 10 is a schematic plan view showing a positional relationship among a mask, a wafer, and an optical system for explaining an alignment method according to an embodiment.
FIG. 11 is a plan view and a cross-sectional view of a wafer holder and a target of an alignment apparatus according to another embodiment.
[Explanation of symbols]
10 Wafer / mask holder
11 Wafer
12 Mask
13A, 13B Wafer mark
14 Mask mark
15 Wafer holder
16 Mask holder
17, 18 Fine adjustment mechanism
20, 60 optical system
21A, 21B Image detection device
22 lenses
23, 26A half mirror
24 optical fiber
25 optical axis
26B mirror
27 Object
28 Relay lens
29A, 29B Imaging plane
30 Control device
31 Deformation compensation means
40A, 40B Image by scattered light from wafer mark
41 Image of scattered light from mask mark
50 base
51 Linear guide
52 Movement mechanism
53 Exposure position
54 Retraction position

Claims (13)

First holding means for holding a first object on which a first mark is formed on a first surface;
Second holding means for holding a second object on which a second mark is formed on the second surface;
The second surface of the second object held by the second holding means is arranged with a gap from the first surface of the first object held by the first holding means. At least a part of the second object held by the second holding means when viewed in a line of sight parallel to the normal direction of the first surface and the normal direction of the first surface. A moving mechanism that moves the second holding means to a second position that does not overlap the first object held by the holding means;
The position of the first mark of the first object held by the first holding means in the direction parallel to the first surface is measured, and the second holding means is the first position. The first mark for measuring the position of the second mark on the second surface of the second object held by the second holding means in the direction parallel to the second surface. A measuring device;
When the second holding means is in the second position, the second holding means is in the direction parallel to the second surface of the second object held by the second holding means and the direction perpendicular thereto. A second measuring device for measuring the position of the two marks;
An alignment apparatus comprising: a fine adjustment mechanism that displaces one of the first object held by the first holding means and the second object held by the second holding means with respect to the other.   The position according to claim 1, wherein the moving mechanism translates the second holding means along a straight line parallel to the first surface of the first object held by the first holding means. Alignment device. The first measuring device, also with respect to the first of the first surface to the vertical direction of the object held in the first holding means, Ru can measure the position of the first mark 請 The alignment apparatus according to claim 1 or 2.   Further, when the moving mechanism is driven, the target surface moves together with the second holding unit and faces the same direction as the second surface of the second object held by the second holding unit, and the target The alignment according to any one of claims 1 to 3, further comprising a stage target having a reference mark formed on a surface, the position of the reference mark being measurable by the first and second measuring devices. apparatus.   Further, when the second holding means is at the first position, the second mark of the second object fixed to the second holding means is measured by the first measuring device. And the second position of the second mark measured by the second measuring device when the second holding means is moved to the second position. The alignment apparatus according to claim 1, further comprising a control unit that drives the moving mechanism and the fine adjustment mechanism based on position information.   The alignment apparatus according to claim 5, wherein the control unit includes a storage unit that stores positional relationship information obtained from the first position information and the second position information.   Furthermore, when the second holding means is at the first position, the first position obtained by measuring the reference mark fixed to the second holding means with the first measuring device. Based on the information and the second position information of the reference mark measured by the second measuring device when the second holding means is moved to the second position. The alignment apparatus according to claim 4, wherein the fine adjustment mechanism is driven.   The alignment device according to claim 7, wherein the control unit includes a storage unit that stores positional relationship information obtained from the first position information and the second position information. (A) placing the third holding means at the third position and measuring the position of the reference mark fixed to the third holding means with a third measuring device;
(B) The third holding means is moved in a direction parallel to the XY plane and arranged at a fourth position , and the reference mark fixed to the third holding means is fixed by the fourth measuring device. Measuring the position;
(C) Based on the two pieces of position information of the reference mark obtained in the step, the position information measured by the third measuring device is associated with the position information measured by the fourth measuring device. A process for obtaining positional relationship information;
(D) The fourth holding means uses the fourth holding means so as to face the third object held by the third holding means when arranged at the third position with a certain gap therebetween. Holding the object of
(E) measuring the position of the fourth mark on the fourth object held by the fourth holding means with the third measuring device;
(F) holding a third object with the third holding means, and moving the third holding means to the fourth position;
(G) With the third holding unit moved to the fourth position, the position of the third mark formed on the third object held by the third holding unit is Measuring with the measuring device of 4;
(H) The third holding means is moved in a direction parallel to the XY plane and arranged at the third position , and based on the positional information of the third mark and the positional relationship information, the relatively moving a third one of the object and the fourth object relative to the other, possess the step of aligning the two,
In the step (a), the position of the reference mark is measured with respect to a direction parallel to the XY plane and a Z direction perpendicular to the XY plane, and in the step (g), a direction parallel to the XY plane, and An alignment method in which the position of the third mark is measured in the Z direction perpendicular to the XY plane, and in the step (h), alignment is performed in the direction parallel to the XY plane and the Z direction .   In the step of aligning the two, the third object is displaced based on the position information of the third mark and the positional relationship information, and then the third holding means is moved to the first holding means. The alignment method according to claim 9, wherein the alignment method is moved to a position of 3. The step (a)
Holding the fifth object provided with the reference mark in the third holding means;
The alignment method according to claim 10, further comprising a step of measuring a position of the reference mark provided on the fifth object held by the third holding means. First holding means for holding a first object on which a first mark is formed on a first surface;
Second holding means for holding a second object having a second mark formed on the second surface;
The second surface of the second object held by the second holding means is arranged with a gap from the first surface of the first object held by the first holding means. At least a part of the second object held by the second holding means when viewed in a line of sight parallel to the normal direction of the first surface and the normal direction of the first surface. A moving mechanism that moves the second holding means to a second position that does not overlap the first object held by the holding means;
A first measuring device for measuring a position of a first mark of the first object with respect to a direction parallel to the first surface of the first object held by the first holding means;
When the second holding means is in the second position, the second holding means is in a direction parallel to and perpendicular to the second surface of the second object held by the second holding means. A second measuring device for measuring the position of the second mark on the second surface of the second object;
When the moving mechanism is driven, it moves together with the second holding means, and by driving the moving mechanism, the first measuring device and the second measuring device are in a direction parallel to the first surface, And a reference mark whose position in the vertical direction is measured,
A direction parallel to the first surface and perpendicular to one of the first object held by the first holding means and the second object held by the second holding means. A fine-tuning mechanism that displaces
An alignment device having The first measuring device also measures the position of the first mark of the first object in a direction perpendicular to the first surface of the first object held by the first holding means. The alignment apparatus according to claim 12.

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